Telephone signaling system



oct. 23, 192s.

c; s. DEMAREsr Er AL TELEPHONE SIGNALING SYSTEI' Filed nay 19, 1926 INVENTORS C. lemals d@ Qoy//zes 7 V i v ATTORNEY Patented' oa. 23, 192s.

PATENT OFFICE.;

CHARLES S. DEMARST, OF RIDGEWOOD, NEW JERSEY, AND OWEN H. LOYNES, OF BROOKLYN, NEWYORK, ASSIGNORS TO AMERICAN TELEPHONE lANI) TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

TELEPHONE SIGNALING SYSTEM.-

Application ined may 19,

Facilities` for the transmission of these' supervisory signals and dialing pulses are sometimes not avallable, as 1n4 Athe case of radio speech channels; and, in the case,of

wire circuits, they cannot always be obtained unlessthere are sacrificed facilities for the transmission of Morse telegraph signals over the telephone circuits. Furthermore,- wlth the present standard facilities for signaling over voice-circuits, certain precautions must be .taken in order to guard againstinterference with the signal currents by the voice currents and in order to reduce the interference from other voice clrcuits and the interference caused in other voice circuits.

It is the object of applicants invention to transmit supervisory signals and dialingl pulses incases in which the facilities cannot be obtained by wire means, as in the case of radio speech channels and, in the. case of wire circuits, to transmit such signals and pulses without any sacri'ce of Morse telegraph facilities, and without any of the types ofl interference mentioned above.

Applicants accomplish. this object bytransmitting all the supervisory signals and all the dialing pulsesfor-a group of voice circuits over a 'common radio channel between the central otlice stations.

The arrangement described below and lshown diagrammatically in the accompanying drawing is one suitable for Atransmitting by applicants means the signals andpulses employedin the toll line dialing method of` operation, in which the operator at the outgoing station can dial directly a subscriber in a distant machine switching area without {irst dialing the distant central oflice board.

With reference to the accompanying drawing, station A is a telephone -central oflice station equipped with dialing apparatus and connected with a distant central oice station B, which is equipped for machine switching,

i926 serial No. 110,253.

by a plurality of voice channels, which may. be ordinary wire circuits, carrier circuits, or radio channels. For the sake of simpl1c1ty,.`the system is shown equipped for operation'only lin the direction station A to station B, that is, for the completion of a call from a subscriber directly connected to (station` A to a subscriber in 'the district of station B. It will be readily understood, however, that in accordance with applicants invention, a system such las that shown `may Abe and normally is equipped for operation in either direction.v

At station A, in association with each j voice channel,-there are the following elements usually found at automatic central cnice stations: a toll cord circuit, an annunciator and a Jack associated with this circuit, dlahng apparatus, and a, switch for connecting this apparatus to the toll cord circuit. At station B there is the u'sual machine swltching equipment, including a line switch andthe district and final selector` apparatus. 1

Ateach station applicants provide means for transmitting radio signals and means for` receiving radio signals, In addition there are associated with each voice channel at each station, means Vfor producing high .frequency signaling current, means for suitably tuning the4 radio receiver, and means for associating the signaling current producers) with the radio transmitting apparatus and for associating the radio receiving apparatus with the signal annunciator (first station) or the machine switching apparatus (second station). For each voice channel served there is required` one radio signaling frequency for signaling in each direction,

. the signaling current'l producer associated with that channel at each station producing an alternating current of a predetermined frequency, and the receiver at Vthe other station being correspondingly tuned by the cir'cuit associated with the channel.

The details of the signaling system willinserts a cord equipped for dialing, into the jack J. Battery fromtheisle'eve of the cord causes relay R1 to operate, andin turn to operate relay R2, which is a -slow release relay. When the operator operates heil key inthe cord circuit which causes the 'dialin equipment at her position to be. associate with the cord, the sleeve of the cord circuit is opened, and relay R1 is permitted to release. With relay R1 released and slow release relay R2 held in its` operated position .by circuit means to ybe described lbelow,

" ground is connected through a back contact 4R, R7 and RB ma of relay R1 and the make contact of relay R2 to a circuit including the windings of relays R3 and R4. Relays R3 and R1 operate and complete the following circuit: battery back Contact of rela R5, windings of relays lie contact of relay R3, lower make contact lof relay R1, over lead R to the cord circuit, through the dialing equi ment in the cord circuit, back over lead and to ground atthe up er make contact of relay R11. Relays R8 an R7 are polar relays RB operatingA when battery is connected to the circuit at relay R5, and R" operating when l battery is connected to the cir cuit. It is understood that neither oi these two relays will res ond to battery of the op-- posite polarity. pon the completion of the ,circuit traced above, relay Rs andthe polar relay Rs will Operate, v The operation of relay R8 holds relay R2 operated after the release of relay R1. The operation of` relay R v. causes the operation of relay R. -`AThe operation of this latter relay connects the oscillator O, which produces a signaling current of high frequency, through t ve tuned-circuit C associated wit-h the voice hannlFunder consideration and the common amplifier'D lto the transmitting antenna at station A from which a lradio signal is sent to station -At station B the initial .radio signal is received from station, A, is changed in freqtlxiency (an oscillator being associated with t e requency changer) and is passed through the common am lier E', the tuned circuit F associated .with the voice channel under consideration and the rectifier G' to the relay R1, which operates.` The operation of relay R1o connects round over the lead M to relay R12 of the lme switch. The

line switch now functions to prepare the 4 automatic switchin equipment to' receive dialing pulses.

relay ofthe line switch. When it` windin of relay R11, a slow operating relay, which oes not operate at this time, as explained below. The operation of relay R13 also closes a circuit from ground through a battery, the'` winding and armature ofthe stepping magnet, the Winding of relay R15, and the armature of relay R1A1 oyer the test lead to ground. The closing of this circuit results in the operation of th'e stepping magnet and also in the operation of relay R1".

path through thel winding of the slow operating relay R14 and'prevents the immediate operation of that relay. The stepping magnet functions in a well-known manner to operatel the brush arms of the line switch in association with corresponding banks of contacts. When an idle sender is found, the test vlead is connected through apparatus not ,shown but well understood in the art and through battery in the district selector mech- .75 The operation of this latter relay breaks the anism to ground, this battery being of such polarity as to oppose the battery in the stepping magnet circuit. The operation of the stepping magnet then ceases. Relay R1 releases, and lrelay R11 operates, placing ground over its' armature to the" test lead for the operationof the necessary busy si al. In addition, the automatic o eration' o the line switch extends the path om the armature of the pulsin relay R12 over the fundamental lead to t e district selector. Also ground from the district selector isv connected over lead S torelay R1". The line switch is now ready to receive the dialing pulses,- andvthe operation of' relay R1 causes the operation of relay R11, which controls the signal transmitter of station B. When relay vR11 operates, -it connects the oscillator O', which produces si aling c urrent of high frequency,.throug the tuned circuit Cf associated with the voice'channel underconsideration and the common ampli- Iier D to the transmitting antenna of station E. It is to be' noted thatduring the o erations described above the initial ,radio signal from station A to station B has been continued,- causin the continued operation of relay R10 and teresponsive operation of R12 inthe line switch. V"

l e responsive radio signal transmitted` from station B, upon the completion of the primar v'operation vof the line switch, lisA receive in the receiving antenna of' station A, is changed in frequency, and is through the common amplifier E', the tuned circuit F lassociated with the voice channel 'under consideration, and the rectifier G to relay R5, which operates. The operatonfof relay R5 disconnects the'armature of that rela' from battery and connects it to 45? battery, that is, it reverses'tle polarity` ob the battery through the dialing equipment, the circuit having been traced above.

This reversal of the batterythrough the passed l lll lll

dialing equipment indicates to the operator at station A that the machine switching equipment at station'B is in condition to receive dialing pulses. She then operates her cord dialing apparatus, causing the` circuit completed through her dialing equipment to be opened intermittently. Relay R, of course, follows the dialing pulses, and

`relay R1 responds, thereby interrupting theradio signal origlnated in oscillator and transmitted to station B." y'

The dialingj pulses transmitted over the radio channel from station A cause the machine switching equipmentat station B to select the subscriber called. This operation is briefly described as follows: Relay .R10 fol-lows the radio signal pulses and connects ground intermittently to the linev switch pulsing relay R12 over lead M. RelayI R12 transmits the pulses over the fundamental lead to the selector apparatus. The machine switching equipment then automatically establishes connection f'rom the leads T and R through the line switch, district selector, and final selector to the called subscribers line. The line switching equipment functions in such a manner as to cause 'ground to be placed over lead S, and through relay R16 over" lead N, before the subscriber removes his receiver (from the 'switch-hook, and to 'be replaced a'f'ter the subscriber returns his receiver to the hook. If the subscriber jiggles his switch-hook, ground is placed intermittently on lead S and on lead'N, and relay R11 is caused to follow the o-peration of the switch-hook.

At station A, while the called subscriber is being rung automaticallyfat station B, relay R1 remains 'operated `jin response to y the continuous' radio signal`- from station B.

Accordingly, the +1 battery is steadily connected to thecircuit through the dialing equipment; and the polar relay R7 is operated, and the polar relay RB is released'. The operation'o relay R7 holds relay R2 operated through a make contact of relayl R2 and the back contact of relay Rs.. When the operator has completed her dialing operations and restores her cord dialing key to normal, a connection is again completed over the sleeve of jack J to relay-R1, which re-operates. Since lrelay R7 is o erated', resistance H is' l connectedv 'to groun 'over .the make contact of relay RT in parallel with relay R1. The( 'value of this resistance H is so chosen that themarginal relay y' in 'the sleeve circuit of l g the toll cord operates and lights the super- I visory lamp L in the toll cord'. v i Then `ith-e called VAfsuloscri 60 through station B,7 the radio signal received R5 at station ber answers .from'station B ceases., and accordingly relay releases, reversing the battery again and Vcausing* the release otpolar .relay R1 and the operation of polar relay Rex The release of relay R7 removes the resistance H from the sleeve circuit, causing the marginal relay in the toll cord to release and extinguish the lamp L. This signal indicates to" the operator at station A that the calledv subscriber has answered through station B. When the called subscribed at station B jiggles4 his switch-hook, relay R5 at station A follows the switch-hook operation, causing relay R7 to respond,placing resistance H in parallel with relay R1 intermittently and causing the flashing lamp L in the toll cord.

lVhen the operator at station A completed the dialing operation and restored her cord dialing key, thereby permitting relay R1y to re-operate, relays R3 and R4 released and connected relay R7 to ground through a make Contact of relay R1. Relay R6 remains operated throughout the period of the connection. Accordingly,relay R2 remains operated, and the radio signal transmitted from oscilla-tor O remains on the signa-ling channel during the abor'e period.

When the. subscriber in the district of stal tion B has finished thecall, ground is automatically placed over lead`S and, throughV the operation of' relay R1, over lead'N -to relay R11, causing a signal to be sent to station A which indicates to the operator at station A that the conversation is completed. She then removes the toll cord fromthe jack J, releasing relays R1, R2, RG, R7 and R9. 'The release of relay R1 results in the discontinuation of the radio signal transmitted to station B land causes the machine-switching equipment at station B to return to normal in response to the releaseof the R12 in the line switch.

' While applicants invention has been disclosed in one specific embodiment which is deemed desirable, it isto beiunderstood thats a voice channel connecting saidl stations, signal announcing'means at the firststation,

pulsing relay.

vof thesupervisory lll() 'irst central automatic line Mselecting andswitching means at the second station, means at each station 'f for generating and transmitting radio signals, means at each station for receiving radio signals transmitted from the other station', automatic means at the first station, responsive to primary'signaling operations lat said station, for operating the radio signal generating and transmitting means at said station to send an initial radio signal to the second'station, automatic means at the second station, `responsive to said initial radio signal received fromthejirst station, for effecting a yprimary operation of the automatic selectingl and switching means,

\ switching *..m'eans at the second station, responsive to automatic means at the -second station, responsive to the termination of said primaryoperation of the selecting -and switching means, for operating -the radio signal generating and transmitting means at said station to send a responsive .primary radio signal to the first station, automatic means at the first station for effecting a-primary operation of the signal announcing means in response to said responsive primary signal received from the` second station, automatic means at lthe first` station, responsive to secondary signaling operations at said station, for operating thel radio signal generating and transmitting means vat said4 station to send a secondary radio signal to the second station, automatic means at the second station,- re; sp'onsive to said secondary signal received from the first station, for effecting a secondary operation of the selecting and eans, automatic means at. the second station. responsive to signaling operations at said station for operating the radiosigna-l t generating and transmitting means at said station to send asecondary radio signalplto the first station, and automatic means at thefirst station for effecting a secondary operation of the signal .announc-` ing means atsaid station in response to said secondary signal received from the second f, station. i

2./In a telephone system, a first central Y office station; a second central ofhce station;

a plurality of 'voice channels connecting said stations; automatic line selecting and switching means at'the second station; means at each station fortransmitting radio signals; means at leach station for receiving radio signals; and the following means associated with each voicecha-nn'el at their respective stations signal announcing means at the first station; means at each station fory produeing radio signaling current o f a' frequency peculiar to thatstation and to the voice channel; means at eaqh station vfor tuning themadio receiving means at that station to the peculiar frequency produced at the other station and corresponding to the voice channel; automatic means at the first station, responsive to primary 'signaling operations at-vsaid station, for connecting the radio signaling'current producing means to the radio signaltransmitting means at said station, causing said transmitting lmeans to send an initial radio' signal,y of thepeculiar frequency, tothe second station; automatic said 4initial radio signal received from .the

first station, for effecting a primary operation of the' automatic ,selecting and lswitching means; automatic means at the second station, responsive to the termination of said primary operation of the` selecting and switching means, for connecting the radio signaling current producing means to the radio signal transmitting means at said station, causing said -t ransmitting means to send a responsive4 primary radio j signal, of the peculiar'v frequency, to the first station; automatic -means at the first station, respons ivel to saidprimary radio signal received from thesecond station, for effecting a primary operation of' the signal announcing means; automatic means at the first station, responsive to secondary vsignaling operations ats aid station, forv connecting the radio signaling current producing means -to the radio signal transmitting means at said station, causing said transmitting means to send a secondary radio signal, of the peculiar frequency, to the second station; automatic means at the 'second station, responsive to said secondary" signal received from the first station, for. effecting 4a secondary operationof the selectingand switching means; automatic means at the second station, responsiveto signalingoperations at said station, for connectingtheradio signaling current producing means to the radio signal transmitting meansfatsaid Station, causing said transmitting means to send a secondary radio signal, ofthepeculiar frequency, to the first station; 'and automatic means at the first station, responsive to said secondary signal received from the second station, for effecting a secondary operation of the signal announcing means at said station.

3. In a' telephone system, a first central office station including .a toll cord circuit, a dialing apparatus and-.an annunciator and a jack alll associated with said circuit, and a switch for connecting the dialing apparatus to, said circuit; a second central office station equipped with machine switching apparatus inclu-ding a line switch; a Voice channel connecting said stations; means at each station"f or .generating and transmitting radioI signals; means at each stat-ion for receiving radio signals transmitted from theK other station; 'automatic means at thelglo first station, 'responsive' tothe connection ofthe toll cord circuitand .the jack and the -received from'the first station',.for causing the operation of the line switch to prepare a path .for the transmissionmof dialing pulses; automatic means at 'said second sta"- .tion-, .responsive vto the-.completion yof said operations ofthe line switch, for operating the radio signal generating andtransmitting means at-said station to'sendnJ radio signal to the first station; automatic means at the first station, responsive tothe reception of' said radio signal from the second station, for reversing the polarity of the current source through thedialing apparatus; automatic means at the iirst ,-station, responsive to the operation of the dialing apparatus', `for interrupting the radio signal transmitted from said station; 'automatic means at the second station, responsive to the interruption of the radio signal received fro the first station, for transmitting dialing pulses over the line switch to cause the machine' switching apparatus to connect the voice channel to the subscribers line associated with said station; automatic meansat the iirst station, responsive to ,the termination of' the operation off the dialing apparatus, for operating the annunciator; automatic means at the second station, responsive to switch-hook signals over the line switch, for operating the radio signal. generating and transmitting means at said/ station to send an interrupted radio signal to the first sta' tion; and autoniaticmeans at the-firstfsta# tion for terminating-the operation of and reoperating the annunciator in response to the reception of said interrupted radio signal from the second stat-ion. i

4. Ina telephone system, a rst central office station; a second central oiiice station, a plurality of voice' channels connecting said -stations; -means at -eacli station for tuning the signal receiving means at that. station to the peculiar frequency produced transmitting radio signals;y means at each station for receiving radio signals; dialing apparatus at `the .first station; machine switching apparatus at the second station, said apparatus'-inc1uding a line switch; and the following `elements and means associated/ with each voice channel atl their respective stations: a toll cord circuit at the first station; an annunciator and a jack associated with said circuit at the first station; a switch for connecting the dialing apparatus to said circuit at the rst station; meansat station for producing signaling current of a frequency peculiar to that station and to the voice channel; means at each station for at the other station and corresponding to the voice channel; )automatic means at the first station, responsive 4to the connection of the toll cord circuit and the jack and the sub-A sequent connection of the dialing apparatus to said circuit; for closing a grounded circuit through the dialing apparatus to a current source of a certain polarity and simultanemeans to send a ra tion, lfor causing the operation of the linev switch to prepare a path for the transmission of dialing pulses; automatic means at said second stat-ion, responsive to the completion of said operation of the line switch, for con-4 necting the signaling current producing means to the radio signal transmitting means at said station, causing said transmitting peculiar frequency, to the first station; automatic means at the first station, responsive to the reception of said radio signal from the second fstation, for reversing the clarity yof the current source through the dia ing apl paratus; automatic means at the firststation, responsivelto the operationof vthe dialing apparatus, for interrupting, in accordance with the operation of said apparatus, the

o signal, of the radio signal, of the peculiar frequency, transmit-ted from said station; automatic means at the second station, responsive to the in'` tgrrup'tion of the radio signa/l, of the predetermined frequency, received from the first station, for transmitting dialing pulses over the line switch to cause the machine switching. apparatus to connect the voice` channel to ythe subscribers line associated with said station; automatic means at the first station, responsive to the termination of the operation Vof the dialing apparatus, for operating the annunciator; automatic means i at -the 4second station, responsive to switch-y hook signals over the line switch, for disconnecting thev current producing means and the radio signal transmitting means at said station and reconnecting the saine in accord `ance with said switch-hook signals, causing saidtransmit-ting` means to send an interrupted. radio signal, of the peculiar `frequency, to the first station; and automatic means at the first station for terminating 'the operation of and re-operating the annunciator in response to the reception of said interrupted radio signal from the second station.4

In testimony whereof, we have signed our names to this specification this 18th day of May, \1926.

\ CHARLES S. DEMAREST. OWEN H. LOYNES.. 

